small change to the generated dartdoc styles (#3290)

dev/docs/styles.html

@@ -10,6 +10,7 @@
     color: #111;
     background-color: #fdfdfd;
     font-weight: 300;
+    -webkit-font-smoothing: auto;
   }
 
   h1, h2, h3, h4, h5, h6 {
@@ -99,6 +100,12 @@
   footer p {
     color: #828282;
   }
+
+  /* Line the material icons up with their labels */
+  i.material-icons.md-36,
+  i.material-icons.md-48 {
+    vertical-align: bottom;
+  }
 </style>
 
 <!-- The following rules are from http://google.github.io/material-design-icons/ -->